1. Field of the Invention
The invention relates to a tube coupling for vehicle air conditioning units.
2. Related Technology
Tube couplings of this type are used, for example, in the tubing system of vehicle air conditioning units. Prior art systems using Freon or R134a as the refrigerant employ tube couplings with one or two O-rings arranged on the coupling plug in grooves.
Due to the arrangement of at least one groove and the conical plug end, a length of the coupling plug results such that, for assembling and disassembling of a tube line section, the metallic tube line section concerned must be correspondingly bent-up. In addition, because of the machining process necessary to form the plug on an extruded profile, the manufacture of the coupling plug requires an effort dependent on the plug length.
O-rings also have the disadvantage of seizing on sealing surfaces due to ageing. The sudden release of the corresponding adhesive forces under the pressure of the confined medium, after unfastening the clamping screw, causes significant danger. The necessary elasticity of the O-rings is advantageous in that they can be easily mounted in the coupling plug's grooves, but the required elastic material of the rings has the disadvantage of a limited sealing effect because of diffusion to be expected, particularly at higher pressures and when sealing certain gases, such as when sealing CO2-systems. When O-ring seals are used in tube couplings exposed to extremely high pressures, there is a danger that the elastic sealing material will be extruded from the sealing groove, particularly when bending forces act on the tube coupling. Further, O-rings in tube couplings are disadvantageous in that the pressure of the medium to be sealed is applied to an area essentially larger in radial direction compared to the area corresponding to the inner diameter of the tubing system so that the tube coupling is exposed to correspondingly high axial forces and must be dimensioned highly massive. Finally, there is a danger that on closing and opening of the tube coupling, the coupling plug, inclusive of its O-ring and hence also sealing surfaces of the coupling socket, may become contaminated or damaged.